As a conventional driving system of the above-described kind, there is proposed a system comprising, for example, a battery serving as a power source of the driving system, a DC/DC converter for applying DC/DC conversion to an input voltage from the battery, a load having an inverter for converting an output from the DC/DC converter into a multi-phase AC current and a motor for rotation driving while receiving the multi-phase AC current from the converter, and a capacitor arranged between the DC/DC converter and the load and connected to the positive and negative bussbars (lines) of the inverter circuit. In such a system, the DC/DC converter applies DC/DC conversion to an input voltage from the battery and the converted voltage is then stored in the capacitor so that the load is driven using the power-stored capacitor then considered as a DC power source.
In this system, while driving control of a DC/DC converter is performed such that the amount of power corresponding to an output required by a load, or “a load requiring output”, can be obtained from the battery, the voltage stored in the capacitor can remain in a stable condition while the driving system can achieve stable driving. General batteries are designed to be capable of supplying an amount of power corresponding to a load requiring output. However, there may be situations in which, depending on the condition of the battery, a battery cannot supply an amount of power corresponding to a load requiring output when, for example, the battery inner resistance has increased due to low battery temperature. Were the DC/DC converter be, in such a case, given driving control simply such that an amount of power corresponding to a load requiring output is fed to the load, power consumption due to inner resistance of the battery may increase, resulting in a drop in power supplied to the load.